1. Field of the Invention
The present invention relates to a simultaneous process for isolation and purification of lutein and zeaxanthin from crude plant oleoresin, preferably marigold extracts with high yield rate.
2. Description of the Prior Art
Carotenoids are yellow, red and orange pigments which are widely distributed in nature. In different fruits and vegetables, there are specific carotenoids, for example, β-carotene in carrots, lutein in marigold flowers, zeaxanthin in strawberry, capsanthin and capsorubin in the pepper plant, and lycopene in tomatoes, etc. Besides xanthophylls in fruits and vegetables, in egg yolks, some fish crustaceans, birds, algae and bacteria, there are also some other carotenoids.
In recent years, human and animal studies have revealed various beneficial effects of carotenoids. Carotenoids are classified into two sub-classes, namely, more polar compounds called xanthophylls or oxy-carotenoids like lutein, zeaxanthin and astaxanthin and non-polar hydrocarbon carotenes like β-carotene, lycopene, etc. Both the sub-classes have at least nine conjugated double bonds which not only are responsible for the characteristic colors of the carotenoids, but also endow them with the function as antioxidants in disease prevention, which may retard or prevent diseases like cancer, arteriosclerosis, cataracts, macular degeneration and others, because carotenoids are effective quenchers of the highly reactive oxygen free radicals and can also prevent generation of free radicals, thereby limiting free radical oxidative damage.
Among kinds of carotenoids, lutein and zeaxanthin recently are paid considerable attention from scientists and public to with respect to their potential role in prevention of an eye disease, namely, Age-Related Macular Degeneration (ARMD). Lutein and zeaxanthin are the only carotenoids present in the macular region of the human retina and are related to a normal function of the macular region responsible for visual acuity (Bone et al. Invest. Ophthalmal. Vis. Sci. 34: 2033-2040, 1993). High consumption of fruits and vegetables riched specifically in lutein and zeaxanthin is correlated to a 43% lower risk of ARMD (Seddon et al. J. Am. Med. Assoc. 272: 1413-1420, 1994) and metabolic pathways for these compounds in the prevention of ARMD have been proposed, too. Food and Drug Administration also considers lutein and zeaxanthin as GARS. Therefore, these carotenoids may be used, individually or in combination, as nutritional supplements and food colorants as well as in clinical trials where their potential health benefits in the prevention of ARMD and cancer can be investigated.
While a process for chemical syntheses of xanthophylls involves multiple steps, and is extremely time-consuming, a more economical route to get large-scale production of xanthophylls is a process that extracts, isolates and purifies xanthophylls from nature sources.
Although being present in many vegetables and fruits such as spinach, broccoli, kale and corn, marigold flowers are the richest sources of lutein, along with other carotenoids, which generally occur esterified with mono- or di-C12-C18 long chain fatty acids such as lauric acid, myristic acid, oleic acid, linoleic acid and palmitic acid.
The xanthophyll esters are extracted from the plant, preferably from marigold flowers and other deep-green vegetables with organic solvents, which themselves were readily removable from the extract. The extract from the petals of marigold flowers (marigold oleoresin) is an excellent resource of lutein esters in large quantities and contains no significant levels of other carotenoids. After saponified under alkaline condition, the xanthophylls in the free form are obtained, the resultant alkali salts of fatty acids obtained from the saponification are removed and the xanthophylls are purified further.
Several patents and publications propose processes for isolation of lutein from marigold petals on a commercial scale. In general, the publications focus on the isolation of lutein in a pure crystal form and involve multiple steps.
U.S. Pat. No. 5,382,714 teaches isolation and purification of lutein from saponified marigold oleoresin by washing with water at a low temperature and then crystallizing in solvent mixtures also at a low temperature. The purification steps are very time consuming and halogenated organic solvent was used, which is not suitable for food or pharmaceuticals.
U.S. Pat. No. 5,648,564 disclosed a process for isolation and purification lutein from marigold oleoresin saponified in alkaline propylene glycol solutions, followed by recrystallization. This process has several disadvantages: firstly, due to high viscosity of the propylene glycol, the saponified and handling process requires a high temperature up to 70° C. for over 10 hours, and this would be harmful for the stabilities of xanthophylls. The following isolation process such as centrifugation or filtration are difficult to be handled, too. Secondly, recovery of lutein is as low as around 59 percent, the content of lutein is not high, too.
U.S. Pat. No. 6,262,284 describes the simultaneous extraction and saponification of carotenoids from marigold dry flower petals with THF, which results in the use of large volumes of solvent, and the solvent also is unstable and so produces may degrade because of being peroxided.
U.S. Pat. No. 6,329,557 develops an industrial scale process for obtaining xanthophyll crystals from marigold oleoresin. The disadvantages of the process are that amounts of organic solvent such as hexane and ketone were used, and these organic solvents are not suitable for food additive.
U.S. Pat. No. 6,380,442 reports a process for isolation of mixed carotenoids from plants, the process is not attractive for commercial applications since more than 30 volumes of water is required for per weight of the input material.
U.S. Pat. No. 6,743,953 employs kinds of organic solvents to isolate and purify xanthophylls from marigold oleoresin. In the process, isopropyl alcohol, ethyl acetate, hexane, acetone and methanol were used, therefore, the method is not welcomed in industrial production.
The disadvantages of these processes described above are that: i) Some toxic organic solvents were used, which were difficult or impossible to remove, resulting in xanthophyll crystals being not suitable for human consumption; ii) It is difficult to handle in the process of isolation or purification because of the high viscosity of solvents and several steps are involved to isolate and succeeded purify the crystals, so it is not attractive for industrial production; iii) There are many steps in the operation, which results in a low recovery of xanthophylls which is usually around 50%.
Thus, there remains a need for an industrial process for obtaining lutein and zeaxanthin concentrates with high purity and as little as possible toxic organic solvent and operation steps, and with high yield rate. The process disclosed herein after will provide such a convenient but effective way to provide a comestible xanthophyll.